Link to Heathrow would add up to £8.7 billion to the cost of HS2

Engineers are considering 11 routes as options to link the HS2 scheme into Heathrow, according to an unpublished report by Arup. The engineering company for HS2 also unveiled that linking the airport would see costs rise between £7.3 billion to £8.7 billion, pushing the project to at least the £40 billion mark.

There are three variables that engineers are assessing: where the HS2 line will first divert towards Heathrow; where the stopping point will be near the airport; and where the loop will rejoin the main line. The report states that "tunnelling considerations are applicable to all elements", and only one surface option – a spur between Heathrow and Denham is being considered. A twin-track tunnel is also proposed, to allow trains to travel underground at speeds of up to 225kph.

Last year Arup lobbied for HS2 to be routed through Heathrow, with a hub station close to Iver, stretching all the way across to Tavistock Road in West Drayton, a proposal rejected by the government last July as it was too expensive. Now, the company at the heart of bringing the 'Heathrow loop' option to life has been tasked by HS2 with integrating the controversial rail line with the busiest passenger airport in Europe.

Depending on which of the 11 possible routes is chosen, residents across some west London boroughs will inevitably face years of disruption while tunnels are bored underneath them. The least costly of the suggested routes is the Denham spur to Heathrow North, at £7.3billion, although if it was tunnelled, it would cost £7.7bn. The route will ultimately come down to HS2, in conjunction with the Department for Transport, who will decide on the basis of cost, political acceptability, disruption and a swathe of other factors. The department has been coy so far on possible routes, and has only said there could be a firm decision next year.

Three stopping points are being considered for HS2 to connect with Europe's largest passenger airport: Iver; Heathrow Terminal 5; and the mysteriously named 'Heathrow North'. Extra platforms are being considered at each, for international provision, with the eventual aim of linking into HS1, which connects to Europe via the Channel Tunnel.

 Heathrow Skyport 21 May